1. Field of the Invention
The present invention generally relates to copolymers. More specifically, it relates to amorphous poly-alpha-olefin (APAO) polymers useful as components in hot melt adhesive formulations.
2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98
Hot melt adhesives (HMAs) are a form of thermoplastic adhesive that is designed to be applied in the molten state. The glue is tacky when hot, and solidifies in a few seconds to about one minute. Hot melt adhesives may also be applied by dipping or spraying.
In industrial use, hot melt adhesives provide several advantages over solvent-based adhesives. Volatile organic compounds are reduced or eliminated, and the drying or curing step is eliminated. Hot melt adhesives have long shelf life and usually may be disposed of without special precautions. Some of the disadvantages involve thermal load of the substrate, limiting use to substrates not sensitive to higher temperatures, and loss of bond strength at higher temperatures, up to complete melting of the adhesive. This may be reduced by using a reactive adhesive that, after solidifying, undergoes further curing—e.g., by moisture (e.g., reactive urethanes and silicones), or is cured by ultraviolet radiation. Some HMAs may not be resistant to chemical attacks and weathering. HMAs do not lose thickness during solidifying; solvent-based adhesives may lose up to 50-70% of layer thickness during drying
Holt melt adhesives of the prior art include rubber-based HMAs, acrylic-based HMAs, silicone-based HMAs, and metallocene polyethylene- and polypropylene-based HMAs.
Amorphous polyolefin (APO/APAO) polymers are compatible with many solvents, tackifiers, waxes, and polymers; they find wide use in many adhesive applications. APO hot melt adhesives have good fuel and acid resistance, moderate heat resistance, are tacky, soft and flexible, have good adhesion and longer open times than crystalline polyolefins. APOs tend to have lower melt viscosity, better adhesion, longer open times and slow set times than comparable Ethylene-vinyl acetate (EVA) copolymers. Some APOs may be used alone, but often they are compounded with tackifiers, waxes, and plasticizers (e.g., mineral oil, poly-butene oil). Examples of APOs include amorphous (atactic) propylene (APP), amorphous propylene/ethylene (APE), amorphous propylene/butene (APB), amorphous propylene/hexene (APH), and amorphous propylene/ethylene/butene. APP is harder than APE, which is harder than APB, which is harder than APH, in accordance with decreasing crystallinity. APOs show relatively low cohesion, the entangled polymer chains have fairly high degree of freedom of movement. Under mechanical load, most of the strain is dissipated by elongation and disentanglement of polymer chains, and only a small fraction reaches the adhesive-substrate interface. Cohesive failure is therefore a more common failure mode of APOs
Amorphous poly-alpha-olefins (APAO) are produced by the (co-) polymerization of α-olefins, e.g. propylene or 1-butene with Ziegler-Natta catalysts. The (co-)polymers have an amorphous structure which makes them useful for the production of hot melt adhesives.
U.S. Pat. No. 5,302,675 to A. Sustic and G. C. Allen describes high tensile strength amorphous 1-butene/propylene copolymers.
U.S. Pat. No. 5,681,913 to A. Sustic and G. C. Allen describes high tensile strength amorphous 1-butene/propylene and ethylene/propylene copolymers.
U.S. Pat. No. 5,637,665 to A. Sustic and G. C. Allen describes high tensile strength amorphous 1-butene/propylene and ethylene/propylene copolymers.
U.S. Pat. No. 5,714,554 to A. Sustic and G. C. Allen describes high tensile strength amorphous 1-butene/propylene and ethylene/propylene copolymers.
U.S. Pat. No. 6,586,543 to H. G. Wey and N. Schlueter describes a process for the preparation of substantially amorphous poly-alpha-olefins.
U.S. Pat. No. 4,309,522 to J. Dietrich, W. Dittmann, A. Frese and W. Kilian describes a process for the production of extensively amorphous butene-1-propene-ethene terpolymers having a high softening point.
U.S. Pat. No. 4,322,514, to M. Miyoshi, K. Matsuura and Y. Tajima describes a process for preparing a copolymer.
U.S. Pat. No. 4,415,718 to M. Miyoshi, K. Matsuura and Y. Tajima describes a terpolymer produced from ethylene, propylene and butylene-1.
U.S. Pat. No. 8,551,270 to Previty et al. describes a pressure-sensitive shrink label.
The following references describe the synthesis of 1-hexene-containing terpolymers:
U.S. Pat. No. 3,954,697 to McConnell, et al. and entitled “Poly(higher-1-olefin-co-propylene) copolymers as hot melt, pressure sensitive adhesives.”
U.S. Pat. No. 4,072,813 to McConnell et al. and entitled “Poly(higher-1-olefin/1-butene) copolymers as hot melt pressure-sensitive adhesives.”
U.S. Pat. No. 4,259,470 to Trotter et al. and entitled “Propylene/1-butene or 1-pentene/higher 1-olefin copolymers useful as pressure sensitive hot melt adhesives.”
U.S. Pat. No. 4,264,756 to Trotter et al. and entitled “Substantially amorphous olefin copolymers and compatible tackifying resins useful as hot melt pressure sensitive adhesives.”
U.S. Pat. No. 4,826,939 to Stuart and entitled “Highly Amorphous Olefin Terpolymer.”
U.S. Pat. No. 5,274,037 to Miller and entitled “Elastomeric Composition Containing Elastomer and Amorphous Propylene/Hexene Copolymer.”
U.S. Pat. No. 5,262,216 to G. H. Popat and T. Mammen describes a pressure sensitive label assembly wherein a propylene-co-hexene-1 copolymer is used in a formulated form.
U.S. Pub. No. 2010/0059178 by Peijun Jiang et al. describes polyolefin adhesive compositions.
European Patent Application EP 0211311 describes a self-adhesive absorbing article and a method for the preparation of a hot-melt adhesive.
U.S. Pat. No. 6,872,279, to Kolowrot, et al., describes a sprayable hot melt adhesive.
U.S. Pat. No. 6,653,385, to Wang et al. describes a hot melt adhesive composition based on a blend of amorphous poly alpha olefin and syndiotactic polypropylene.
U.S. Pat. No. 7,517,579, Campbell et al., describes tackified amorphous poly alpha olefin bonded structures.